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  Subjects -> ENGINEERING (Total: 2278 journals)
    - CHEMICAL ENGINEERING (190 journals)
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CHEMICAL ENGINEERING (190 journals)                     

Showing 1 - 0 of 0 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 5)
ACS Sustainable Chemistry & Engineering     Hybrid Journal   (Followers: 3)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 5)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Advanced Chemical Engineering Research     Open Access   (Followers: 30)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 5)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24)
Advances in Chemical Engineering and Science     Open Access   (Followers: 52)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 7)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 15)
Biofuel Research Journal     Open Access   (Followers: 4)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 7)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
Chemical and Engineering News     Free   (Followers: 12)
Chemical and Materials Engineering     Open Access   (Followers: 10)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 12)
Chemical and Process Engineering     Open Access   (Followers: 23)
Chemical and Process Engineering Research     Open Access   (Followers: 20)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 32)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 16)
Chemical Engineering Communications     Hybrid Journal   (Followers: 13)
Chemical Engineering Education     Full-text available via subscription  
Chemical Engineering Journal     Hybrid Journal   (Followers: 32)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 21)
Chemical Engineering Research Bulletin     Open Access   (Followers: 10)
Chemical Engineering Science     Hybrid Journal   (Followers: 22)
Chemical Geology     Hybrid Journal   (Followers: 16)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 159)
Chemical Society Reviews     Full-text available via subscription   (Followers: 41)
Chemical Technology     Open Access   (Followers: 14)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Industry     Hybrid Journal   (Followers: 4)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry of Materials     Full-text available via subscription   (Followers: 166)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 4)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
CORROSION     Full-text available via subscription   (Followers: 20)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 6)
Current Opinion in Chemical Engineering     Open Access   (Followers: 8)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription   (Followers: 2)
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 6)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 2)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Heat Exchangers     Open Access   (Followers: 3)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 10)
Indonesian Journal of Chemical Science     Open Access   (Followers: 1)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 11)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 22)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access   (Followers: 1)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 4)
International Journal of Waste Resources     Open Access   (Followers: 3)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 3)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 6)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 12)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 113)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription   (Followers: 1)
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 7)
Journal of Chemical Engineering     Open Access   (Followers: 17)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 14)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Crystallization Process and Technology     Open Access   (Followers: 8)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 3)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access   (Followers: 1)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal   (Followers: 1)
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 8)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 5)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 8)
Journal of Organic Semiconductors     Open Access   (Followers: 5)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 4)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 9)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 6)
Journal of Polymers     Open Access   (Followers: 3)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 277)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 8)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 1)
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Konversi     Open Access  
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 15)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 2)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 4)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 1)
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 113)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 15)
Polyolefins Journal     Open Access  
Powder Technology     Hybrid Journal   (Followers: 14)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 60)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 3)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 2)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [22 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3039 journals]
  • Molecular characterization of petroleum fractions using state space
           representation and its application for predicting naphtha pyrolysis
           product distributions
    • Abstract: Publication date: 8 June 2017
      Source:Chemical Engineering Science, Volume 164
      Author(s): Hua Mei, Hui Cheng, Zhenlei Wang, Jinlong Li
      Molecular model of petroleum fractions plays an important role in the designing, simulation and optimization for petrochemical processes such as pyrolysis process, catalytic reforming and fluid catalytic cracking (FCC). However, it is very difficult to exactly characterize the composition distributions due to its internal complexity and containing numerous redundant information and measuring errors although many efforts have been made so far. As an improvement of the work in Mei et al. (2016), a molecular-based representation method within a multi-dimensional state space is developed in this paper. In this method, each pure component in the petroleum mixtures is defined as a state variable and any petroleum fractions can be geometrically represented as a point in a multi-dimensional linear state space, in which a conception of basis fractions is further introduced by defining a group of linear independent vectors so that any petroleum fractions within the specified range (e.g. naphtha) can be obtained through a linear combination by such basis fractions. The redundant information and measuring errors in the pre-determined petroleum fraction samples are eliminated through the procedure of calculating the basis fractions with non-negative matrix factorization (NMF) algorithm, meanwhile the scale of the feedstock database is highly decreased. As an application example of the basis fractions, a quick prediction approach on naphtha pyrolysis product distributions is developed by linearly combining the pyrolysis products of the basis fractions. In contrast to mechanistic models, this proposed method is more suitable for real-time control and optimization purpose with little loss of accuracy.

      PubDate: 2017-02-16T09:22:48Z
       
  • Oil detachment mechanism in CO2 flooding from silica surface: Molecular
           dynamics simulation
    • Abstract: Publication date: 8 June 2017
      Source:Chemical Engineering Science, Volume 164
      Author(s): Timing Fang, Muhan Wang, Chao Wang, Bing Liu, Yue Shen, Caili Dai, Jun Zhang
      Adopting molecular dynamic simulations, the displacing behavior of the adsorbed oil on silica surface by CO2 at different temperatures (303K, 323K, 343K, 363K and 383K) were studied. The density profile, tortuosity distribution, diffusion coefficient and radial distribution functions were chosen to characterize the microscopic detachment process, and two distinct displacement modes of the adsorbed oil, layer-by-layer and entire detachment, were identified at different temperatures. In addition, at temperature 343K, the highest diffusion capability of the adsorbed oil was found to be responsible for a best detachment performance. Our work provided a molecular-level understanding of oil detachment behavior in CO2 flooding at different temperatures, and the results have some promise for enhancing oil recovery in CO2 displacing engineering.
      Graphical abstract image

      PubDate: 2017-02-16T09:22:48Z
       
  • On the fluid mechanics of slotted liners in horizontal wells
    • Abstract: Publication date: 8 June 2017
      Source:Chemical Engineering Science, Volume 164
      Author(s): Mohan Sivagnanam, Jingyi Wang, Ian D. Gates
      Slotted liners are flow control devices widely used in both injection and production wells for thermal oil sands recovery operations such as Steam-Assisted Gravity Drainage. In these devices, slots are cut into the well at regular intervals around and along the well. The dimensions tend to be from fractions to several millimeters in gap and a few to about twenty centimeters long along the pipe. The key benefits offered by slotted liners are that they are among the most economical solutions for sand control and well bore stability as well as manufacturing. Slotted liners have several design parameters including the slot density, pattern, slot opening size and shape that must be chosen to provide optimum inflow and outflow performance in the reservoir. Due to the complexity in deriving these parameters analytically or experimentally, we have examined the impact of design parameters on steam injection by using a realizable k-ε turbulence computational fluid dynamic model of a 5m slotted liner section coupled to a reservoir flow domain outside of the well governed by a modified Darcy’s law that accounts for inertial effects. The results reveal that slot open area affects the flow distribution in the reservoir. The role of drive forces changes through the flow with viscous and pressure forces dominant in the slot and upstream area and inertial forces just downstream of the slot and pressure and viscous forces in the reservoir.

      PubDate: 2017-02-16T09:22:48Z
       
  • Diffusion of charged nano-disks in aqueous media: Influence of competing
           inter-particle interactions and thermal effects
    • Abstract: Publication date: 8 June 2017
      Source:Chemical Engineering Science, Volume 164
      Author(s): Yogesh M. Nimdeo, Yogesh M. Joshi, K. Muralidhar
      In this work we investigate binary mass diffusion of negatively charged disk-shaped nanoparticles of Laponite JS in ultrapure water using Mach-Zehnder interferometry aided by a sensitivity analysis. We observe that binary mass diffusivity of aqueous suspension shows a consistent enhancement with concentration of Laponite at a given temperature. The dependence on temperature, however, is observed to be non-monotonic, wherein the binary mass diffusivity first increases with temperature up to 20°C while decreasing at higher temperatures. We propose that the observed non-monotonic dependence of binary diffusivity on temperature is due to competing effects such as: thermal energy of Laponite particles, that of counterions, and the magnitude of charge on the Laponite particles. These factors affect the aggregation rate of Laponite particles leading to the behaviour observed in the experiments. Interestingly the binary diffusivity of Laponite obtained in the present work is significantly higher than the self-diffusion coefficient of a corresponding hard disk. We propose that enhanced binary diffusivity is due to repulsive interaction among the Laponite particles that augments mobility of the solute in ultrapure water.
      Graphical abstract image

      PubDate: 2017-02-16T09:22:48Z
       
  • Comparison of turbulence models for bubble column reactors
    • Abstract: Publication date: 8 June 2017
      Source:Chemical Engineering Science, Volume 164
      Author(s): Zoheb Khan, Vishal H. Bhusare, Jyeshtharaj B. Joshi
      Though bubble column reactors are widely used in industry, the present design practice is still closer to an art than a desired state of science because of the complexity of its fluid mechanics. The empiricism can be reduced by understanding detailed flow pattern, turbulence characteristics and turbulent structures and their effects on the performance such as mixing and axial mixing in both the phases and rate of heat and mass transfer. For this purpose, in the present work, CFD simulations have been undertaken by using standard k-ε, RSM and LES turbulence models. The cylindrical column having a computational height of HD =900mm with inside diameter of D=150mm was employed as a bubble column operated at three superficial gas velocities (20, 40 and 100mm/s). The instantaneous three dimensional velocity field is obtained by means of two phase Eulerian-Eulerian Large Eddy Simulations (LES). The conservation equations for turbulent kinetic energy (k) and the turbulent energy dissipation rate (ε) have been derived from the two fluid governing equations using the Reynolds averaging procedure. This enabled accurate estimation of convective transport, diffusive transport, turbulent transport, production and dissipation of k and ε. These estimations have been compared with the modelled terms of the standard k-ε and Reynolds stress models. The difference in values gives an idea about the severity of assumptions made in these models. An attempt has been made to bring out the implications of simplifying assumptions.

      PubDate: 2017-02-16T09:22:48Z
       
  • Markovian and Non-Markovian sensitivity enhancing transformations for
           process monitoring
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Tiago J. Rato, Marco S. Reis
      Process monitoring is a key activity in modern industrial processes. Even though abnormality detection can be rather effectively done with resort to acausal correlation models of the variables normal operating conditions associations, fault diagnosis and troubleshooting do require causal information. In this article, we propose a new plug-in approach that brings the causal network structure into a classical monitoring scheme based on the Hotelling’s T 2 methodology. The modular plug-in nature associated to a well-known monitoring scheme aims at facilitating the access to the benefits of using more information about the system structure in fault analysis and diagnosis. The pre-processing module consists of a Sensitivity Enhancing Transformation (SET) that incorporates the network structure inferred from normal operation data, which has recently conducted to significant improvements for monitoring the correlation structure of industrial processes. Additionally, we consider both Markovian and Non-Markovian network structures in the development of the SET. The proposed methodology was tested with two simulated case studies (a CSTR and the Tennessee Eastman benchmark) and compared with several alternative approaches. The results obtained recommend the use of the static Non-Markovian SET as pre-processing for the Hotelling’s T 2 methodology.

      PubDate: 2017-02-10T13:52:07Z
       
  • Exhaust gas fuel reforming for hydrogen production with CGO-based precious
           metal catalysts
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Seunghyeon Choi, Joongmyeon Bae, Juhun Lee, Jeonghwa Cha
      This paper investigated the fuel reforming of exhaust gases with Me/Ce0.9Gd0.1O3-d catalysts (Me=Pt, Rh, Ru). The reaction characteristics of the exhaust gas reforming reaction were evaluated by modifying certain reforming conditions, including the temperature, composition of the exhaust gas, hourly space velocity of the gas, and the amount of exhaust gas used. Using lean-burn exhaust gas, iso-octane and gasoline reforming were first investigated with a traditional liquid fuel reforming catalyst, Pt/CGO (0.5wt.%). The highest yield of hydrogen was obtained when the exhaust gas ratio was approximately half the fuel ratio in this study. Moreover, the hydrogen yield was maximized at temperatures over 700°C and a GHSV of approximately 10,000/h. In commercial gasoline tests, catalytic degeneration occurs under 700°C, and carbon deposition occurs even with small deficiencies of the exhaust gas. Therefore, other precious metal catalysts were investigated for lower-temperature operation. In lower-temperature operation at approximately 600°C, the Ru/CGO catalyst exhibited better performance in exhaust gas reforming than other noble metal catalysts.

      PubDate: 2017-02-10T13:52:07Z
       
  • The role of fouling in optimizing direct-flow filtration module design
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Mylène Wang, Sourav Mondal, Ian M. Griffiths
      The local transmembrane pressure (TMP) distribution plays a crucial role in the performance of hollow-fiber microfiltration and ultrafiltration membrane devices. A direct-flow filter comprises an array of hollow fibers encased within a single module. The TMP in each hollow fiber is dependent on the spacing between neighboring fibers, and evolves with time due to pore clogging by contaminants (fouling). We consider an idealized set-up in which the fibers are undeformable and equally spaced within the device, and study the impact of the pore-blocking phenomena on the TMP during the filtration process. The model is used to evaluate the optimum inter-fiber spacing that maximizes the fluid processed either after a prescribed time or before the filter blocks and its dependence on the membrane permeability and the fouling rate. We show that significant improvements can be made on the operating efficiency of a direct-flow device through careful choice in the fiber spacing during fabrication.

      PubDate: 2017-02-10T13:52:07Z
       
  • Evolution of internal flows in mechanically oscillating sessile droplets
           undergoing evaporation
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Apratim Sanyal, Saptarshi Basu
      Sessile water droplets on hydrophobic substrates have been subjected to mechanical oscillations to excite mean streaming flows in the liquid phase. The driving frequencies are below 1kHz. The flow features have been imaged at a frame rate much lower than the driving frequencies. Counter-rotating vortices are observed along the oscillating liquid-vapor interface (droplet free surface) while an upward drift originating from the substrate exists in the interior. The mean flow features arise out of steady streaming from the substrate and the oscillating liquid-vapor interface. The upward drift is segregated along the droplet height by seemingly horizontal planes. These planes are a characteristic of the time periodic velocity rather than the mean flow. Furthermore when the oscillating droplet is allowed to evaporate under stationary ambient conditions and constant driving frequency, these flow features evolve in a spatio-temporal fashion. In one of our previous studies, we have shown that the oscillation mode of the droplet changes when allowed to evaporate. Mode transition therefore also leads to evolution of the mean streaming flow. The aim is to provide a physical understanding of the evolution of the time averaged flow. This work is motivated by studies related to manipulation of nano-particle deposition patterns in colloidal droplets using controlled oscillations.

      PubDate: 2017-02-10T13:52:07Z
       
  • Numerical investigation and comparison of coarse grain CFD – DEM and TFM
           in the case of a 1MWth fluidized bed carbonator simulation
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): A. Nikolopoulos, A. Stroh, M. Zeneli, F. Alobaid, N. Nikolopoulos, J. Ströhle, S. Karellas, B. Epple, P. Grammelis
      This work focuses on a comparison between the Euler-Euler Two Fluid Model (TFM) approach and the coupled coarse grain discrete element CFD-DEM numerical model for the simulation of a 1MWth CFB carbonator reactor located at TU Darmstadt (TUD). The effect of the drag force formulation and its associated application in the numerical model for both approaches in terms of their numerical accuracy, compared to experimental data is investigated, by implementing either the conventional Gidaspow model or the advanced EMMS one. Moreover, for the coarse grain CFD – DEM model, the range of values for important numerical parameters as the particle per parcel and cell to parcel size ratios are investigated to shed light on the necessary resolution such a model should have in order to reproduce valid and not parameter dependent numerical results. An adequate cell length to parcel diameter ratio is found to be around 2.6 while as concerns the parcel to particle diameter ratio a value around 58.5 proved to be sufficient, at least for the range of parameters investigated in this paper (size of riser, flow rates and particles average diameter). The EMMS model improved the accuracy of results derived by the coarse grain CFD – DEM model, while further research on the appropriate drag models for the coarse grain CFD – DEM is a sine qua non for its successful implementation in similar studies. For instance it is of interest to answer whether the individual particles slip velocity instead of the particles cell averaged slip, should be used for the calculation of the momentum interexchange coefficient (β) as well as the treatment of different particle diameters in the EMMS equation scheme.
      Graphical abstract image

      PubDate: 2017-02-10T13:52:07Z
       
  • The effect of particle surface charge density on filter cake properties
           during dead-end filtration
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Søren Lorenzen, Kristian Keiding, Morten L. Christensen
      During the filtration of suspended organic material, filter cakes with high specific resistances are often formed. The properties of these filter cakes differ markedly from the classical filtration properties derived from inorganic suspensions, not only by having a higher specific resistance but also by being highly compressible. These organic substances typically have a high surface charge density, due to the different functional groups on their surfaces, so a set of model particles was synthesized in which the surface charge density can be varied while keeping all other properties constant. The synthesized monodisperse particles all have a polystyrene core and varying ratios of charged (i.e. polyacrylic acid) and uncharged (i.e. hydroxypropyl cellulose) stabilizing polymers covalently grafted to the surface. All used particles have proven to be stable against aggregation during storage and are easily redispersed upon agitation. Aqueous suspensions of the particles were filtered in a dead-end setup at constant pressure to determine the filter cake properties. Results indicate that the specific cake resistance, cake compressibility, and cake porosity increase with the particle surface charge. Comparison with two empirical models of filter cake resistance demonstrates that particle charge is more important than is porosity, as highly charged filter cakes have resistances orders of magnitude higher than calculated, which is not the case for filter cakes of uncharged particles. DLVO theory suggests that the results cannot be explained in terms of classical double-layer effects, even in the extreme case of very small interparticle distances. Deviations from this classical behavior, arising from the confinement of charged particles by charged walls or pores, are a possible explanation, allowing the high resistances to be interpreted as increased osmotic pressure due to the distribution of counterions in the pores. Calculations indicate that osmotic pressure increases with particle charge and with decreasing porosity, but remains close to zero for uncharged particles.

      PubDate: 2017-02-04T10:35:04Z
       
  • Application of the dynamic flow sheet simulation concept to the
           solid-liquid separation: Separation of stabilized slurries in continuous
           centrifuges
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Marco Gleiss, Simon Hammerich, Michael Kespe, Hermann Nirschl
      In recent years, the concept of flow sheet simulation of fluid processes has been extended to the dynamic performance of solids handling by considering the particle size distribution as one relevant material property. Continuous centrifugation is widely used throughout the process industry and applied to separate finely dispersed particles from a liquid phase. Current process simulation tools for calculation of separation in decanter centrifuges are limited to steady-state conditions and are currently not applicable for real time simulations. This work illustrates the basic framework of a new dynamic flow sheet approach to predict the clarification process of stabilized particles in decanter centrifuges. The solids residence time distribution describes the transient behavior of a lab decanter centrifuge. This allows the simulation of the complex process behavior with small numerical effort. In the presented approach, the number of related compartments is one key parameter. It could be shown that the concept is suitable for real time simulations of decanter centrifuges. The presented numerical algorithm is capable of real time simulations and model-based process control of a lab decanter centrifuge. This is guaranteed by connecting the solids residence time distribution with the properties of the material for the sedimentation and sediment build-up. The accuracy of the new approach is shown by comparing numerical simulations with experimental results. The presented model is unsuitable to predict the sediment solids concentration of a material which forms a compressible cake. An extension of the basic framework to tubular centrifuges or filter centrifuges is also applicable by considering the solids residence time distribution of these types of machines, the properties of the processed materials and neglecting the sediment transport.
      Graphical abstract image

      PubDate: 2017-02-04T10:35:04Z
       
  • A new hydrate deposition prediction model for gas-dominated systems with
           free water
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Zhiyuan Wang, Jianbo Zhang, Baojiang Sun, Litao Chen, Yang Zhao, Weiqi Fu
      Hydrate deposition is an important issue for flow assurance in subsea pipelines. Current models for hydrate deposition in gas-dominated systems with free water mainly consider hydrate formation in liquid films on pipe walls. However, hydrate particles formed from water droplets in the gas phase may also play a significant role in hydrate deposition. In this work, a new model for predicting hydrate deposition is proposed. This model considers hydrate formation from both liquid film and liquid droplets. In the model, an effective deposition ratio is introduced to calculate the deposition of hydrate particles from the gas phase by considering the influence of liquid film atomization. The simulation results agree well with the experimental data. It is indicated that the deposition of hydrate particles formed by liquid droplets in the gas phase has a significant influence on the reduction of the flow passage in the pipeline. By using the new model, the non-uniform distribution of the flow passage at different times and locations can be obtained, and the most vulnerable position for hydrate deposition can be predicted. The model predicts the risk of hydrate deposition more reliably than current methods and provides helpful advice for the prevention of hydrate deposition in the field.

      PubDate: 2017-02-04T10:35:04Z
       
  • Pilot scale production, kinetic modeling, and purification of glycine
           betaine and trehalose produced from Actinopolyspora halophila (MTCC 263)
           using acid whey: A dairy industry effluent
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Jayaranjan R. Kar, Rekha S. Singhal
      Dairy factories manufacturing Greek yoghurt generate huge quantities of acid whey, an effluent which has serious ecological ramifications. In this work, we have used Actinopolyspora halophila (MTCC 263), an extreme halophile that utilized acid whey for pilot scale production of glycine betaine and trehalose which are commercially important compounds having innumerable applications in many industries. Batch bioreactor process with 200rpm agitation and 3vvm aeration gave a maximum production of 13.57±0.39gL−1 glycine betaine and 5.09±0.19gL−1 of trehalose. Kinetic models were also evaluated for production (biomass, glycine betaine and trehalose) and substrate utilization (lactose, glycine and total nitrogen) in A. halophila. Screening of resins for chromatographic separation of glycine betaine and trehalose showed strong cation exchange resin to be the most effective. The recovery of glycine betaine was 86.04±2.86% with purity of 82.26% and that of trehalose was 90.04±1.17% with purity of 94.47%. The findings of this work could benefit the dairy industries to plan on utilization of acid whey and generate revenue while simultaneously preventing environmental and economic repercussions caused by it.

      PubDate: 2017-01-27T20:07:24Z
       
  • The lag between micro- and macro-mixing in compressed fluid flows
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Daniel Bassing, Andreas S. Braeuer
      We report the application of a novel optical Raman-based measurement technique for the simultaneous determination of the progress of mixing on the micro- and on the macro-scale. The introduced measurement technique is applicable to mixing systems containing one compound, which potentially can form hydrogen bonds, such as water, alcohols or amines, and does not rely on the addition of traces of indicator compounds. Here we demonstrate its applicability by analyzing the lag of micro-mixing behind macro-mixing when liquid ethanol is injected into a supercritical bulk environment mainly composed of carbon dioxide (CO2). While the degree of mixing on the macro-scale is determined from the ratio of the intensities of characteristic Raman signals of ethanol and CO2, the degree of mixing on the micro-scale is determined from the shape of the OH stretching vibration Raman signal of ethanol, which is a function of the development of hydrogen bonds.
      Graphical abstract image

      PubDate: 2017-01-27T20:07:24Z
       
  • Modeling the micromechanical interactions between clathrate hydrate
           particles and water droplets with reducing liquid volume
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Chenwei Liu, Yuxing Li, Weiyang Wang, Sanbao Dong, Mingzhong Li
      The micromechanical interactions between hydrate particles and water droplets play an important role in determining hydrate agglomeration, which is a crucial cause of hydrate blockages/bedding in deepwater gas-oil flowlines. The amount of hydrate converted from water droplet during the interaction between hydrate particles and water droplets led to the reduction in liquid volume, which would significantly affect the interaction forces. The existing classic pendular liquid bridge model with fixed liquid volume is not adequate for this unique case. In this study, a modified pendular liquid bridge model has been developed by considering the conversion of hydrate from liquid droplet. Parabolic approximation and a rupture criterion are proposed to determine the liquid bridge profile and rupture distance, respectively. On the basis of experimental observations, the capillary force model between two plates is applied to predict the interaction forces. It is found that the evolution of the profile of bridge (including the hydrate coating section and the pure liquid section) can be predicted with a satisfactory accuracy. Subsequently, it ensures the good agreement between the measured and predicted interaction forces. The profile of the liquid bridge becomes unstable just before the rupture of the liquid bridge, resulting in a large deviation between the experimental results and the model predictions. The proposed model can be successfully used for investigating the effects of different factors, such as contact area and hydrate formation rate, on the interaction behavior/forces, which could help to provide new and critical insights into the hydrate agglomeration process. The developed models contribute a significant progress in existing models development on hydrate agglomeration, and thus could provide a more accurate evaluation of hydrate formation risk in gas-oil flowlines.

      PubDate: 2017-01-27T20:07:24Z
       
  • Investigation on the dissociation flow of methane hydrate cores: Numerical
           modeling and experimental verification
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Lin Chen, Hikaru Yamada, Yuki Kanda, Junnosuke Okajima, Atsuki Komiya, Shigenao Maruyama
      Methane hydrate has become one of the important topics in recent years as there are more and more reports on possible actual production systems. The most challenging problem for stable methane hydrate production from sea beds or under permafrost regions lies in the complex flow and transportation process, which usually occurs inside the unconsolidated porous layers. The current study is focused on laboratory-scale explorations of the basic dissociation behaviors of methane hydrate. A high-pressure experimental system for the methane hydrate synthesis and dissociation process has been established in this study. The experimental system is specially designed to form and store the methane hydrate under high pressure and low temperature conditions. The mixing of sand with the formed methane hydrate makes it possible to control the initial saturation for dissociation in the current study. A numerical simulation model for core-scale dissociation flow has also been set up, and good agreement with the experimental data was found. It is found that the dissociation on a core scale is more heat-transfer controlled. Through comparisons with previous experimental and numerical results, it is known that the operation strategy will significantly affect the dissociation parameter behaviors. The effects of the initial temperature and permeability on the dissociation process are also shown in this study. Future considerations of core-scale models and reservoir-scale production strategies are also discussed in detail.
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      PubDate: 2017-01-27T20:07:24Z
       
  • Reaction kinetics and equilibrium parameters for the production of
           oxymethylene dimethyl ethers (OME) from methanol and formaldehyde
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Dorian Oestreich, Ludger Lautenschütz, Ulrich Arnold, Jörg Sauer
      A catalyst screening comprising zeolites and ion exchange resins for the synthesis of oligomeric oxymethylene dimethyl ethers (OME) from methanol (MeOH) and formaldehyde (FA) has been carried out. All catalysts led to the same product spectrum and parameters for chemical equilibrium have been determined. The ion exchange resin Dowex50Wx2 showed highest activity and reaction kinetics has been investigated employing this catalyst. The influence of the FA:MeOH ratio and water as well as refeeding of OMEs with undesired chain lengths have been considered in the kinetic model, which is based on a hyperbolic approach. Experiments have been carried out in the temperature range between 40 and 120°C and variable FA:MeOH ratios from 0.5 to 1.5g/g have been employed. Regarding water, up to 23wt.% have been added to the reaction mixtures to investigate its influence on yield and reaction rate. Low water contents lead to high OME selectivities. By varying the FA:MeOH ratio, chain lengths of the OMEs can be influenced. Regarding the most active catalyst Dowex50Wx2, 90% of equilibrium conversion is reached after 5min at 60°C employing a catalyst loading of 1wt.%. A study on the long term performance of the catalyst has been carried out and after 17days the decrease of activity was below 10% while selectivity remained the same. For different Dowex catalysts a general kinetic model could be developed, which is not limited to Dowex50Wx2.
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      PubDate: 2017-01-27T20:07:24Z
       
  • Role of local geometry on droplet formation in axisymmetric microfluidics
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Liangyu Wu, Xiangdong Liu, Yuanjin Zhao, Yongping Chen
      An unsteady model of droplet formation in co-flow and flow-focusing microfluidics is developed and numerically analyzed to investigate the dynamic behaviors of droplet formation in axisymmetric microfluidics with a focus on the role of local geometry. The effects of capillary number and local geometry on the droplet formation regimes, droplet sizes and monodispersity as well as droplet generation frequency are examined and analyzed. Once identified, a drop formation regime diagram is provided to quantitatively describe the respective regime of dripping, dripping-jetting transition, and jetting in axisymmetric microfluidics, depending on the Capillary number and orifice radius. The results indicate that, the existence of focusing orifice induces a strong hydrodynamic focusing effect, causing the droplet formation behaviors in flow-focusing microfluidics depart from the co-flow one. The dripping-jetting transition regime occurs at a smaller Capillary number in flow-focusing microfluidics, and the droplets produced by flow-focusing microfluidics are smaller than those in co-flow system with wider size distribution and higher frequency. Interestingly, the droplet formation in flow-focusing microfluidics is significantly affected by the orifice radius while it is insensitive to the orifice length. In addition, when the orifice radius is sufficiently small or the Capillary number is larger than 0.3, only the jetting regime is observed. As the orifice radius increases, the regions of Capillary number for both the dripping-jetting transition regime and dripping regime turn to be larger.

      PubDate: 2017-01-27T20:07:24Z
       
  • Core-shell structured CaO-Ca9Al6O18@Ca5Al6O14/Ni bifunctional material for
           sorption-enhanced steam methane reforming
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Xiangling Chen, Lei Yang, Zhiming Zhou, Zhenmin Cheng
      Sorption-enhanced steam methane reforming (SESMR) is a promising technology for H2 production, which can be further enhanced at the particle scale by using core (sorbent)-shell (catalyst) structured bifunctional materials. However, it is challenging but desirable to develop such materials with high activity and stability. In this work, three core-shell structured CaO-Ca9Al6O18@Ca5Al6O14/Ni bifunctional materials with varying CaO content and core/shell mass ratio were prepared by a two-step sol-gel method, and two others (Ni/CaO and CaO@Ca5Al6O14/Ni) served as references. The structural properties and catalytic performance of the materials were investigated. The results showed that all core-shell materials during cyclic SESMR operation had much better performance than Ni/CaO with regards to activity, stability and CaO utilization, and CaO-Ca9Al6O18@Ca5Al6O14/Ni was generally superior to CaO@Ca5Al6O14/Ni except when the former had a much higher CaO content than the latter. The excellent performance of CaO-Ca9Al6O18@Ca5Al6O14/Ni was mainly due to the stabilization effect of Ca9Al6O18 and the support effect of Ca5Al6O14. The best material was a CaO-Ca9Al6O18@Ca5Al6O14/Ni with a CaO content of 13wt% and a core/shell mass ratio of 0.2, showing high activity and stability over 60 SESMR cycles while maintaining nearly complete utilization of CaO.
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      PubDate: 2017-01-27T20:07:24Z
       
  • The influence of backpressure on severe slugging in multiphase flow
           pipeline-riser systems
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Chen Xie, Liejin Guo, Wensheng Li, Hongliang Zhou, Suifeng Zou
      Severe slugging is a well-known instability in multiphase flow through a pipeline-riser system that is characterized by sharp pressure changes and violent flow fluctuations. This can cause safety and operational problems in the production of oil and gas. Particularly for deepwater risers, which can be up to 3000m long, the operating pressure in the pipeline and riser can be high (that is a few hundreds of bar). Most lab experiments carried out so far for severe slugging were conducted at atmospheric pressure. The present study contains new experiments at elevated pressure. Thereto a new large-scale pipeline-riser system was established with 300bar maximum pressure. To study the effect of the pressure at the riser top on severe slugging, experiments for the stability boundaries and for the amplitude and frequency of the slugging were carried out for pressures in the range of 0–50barg. The results show that an increased backpressure gives a reduced region of severe slugging in the flow pattern map, whereas it also mitigates pressure fluctuations and decreases the slug frequency. Based on these experimental results, the existing prediction model for the stability of steady state operation and the transition to severe slugging was modified to incorporate the effect of the backpressure.

      PubDate: 2017-01-27T20:07:24Z
       
  • Determination of the flow field inside a Sonolator liquid whistle using
           PIV and CFD
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): David J. Ryan, Mark J.H. Simmons, Michael R. Baker
      PIV experiments and CFD simulations were carried out on a mimic of a pilot scale Sonolator Model A inline liquid whistle mixer (Sonic Corp. USA) for water in turbulent flow for Reynolds numbers at the orifice between 17,500 and 77,200. Three different sizes of orifice were used. The results from PIV were compared with the CFD simulations, with both global and local validations being performed. The former focusses on the pressure drop across the Sonolator and the latter was carried out by comparison of local values of velocity magnitude, turbulent kinetic energy and local specific turbulent energy dissipation rate. Velocity magnitude values were found to agree within 10% more than fifteen millimetres downstream of the orifice. A similar level of agreement was found at the orifice for lower flow rates and larger orifices. Factors which precluded this level of agreement for higher flow rates and smaller orifices were the appearance of cavitation and a minimum achievable laser pulse separation, limiting the maximum velocity measureable by the PIV. Agreement between PIV and CFD was also poorer for the turbulent parameters, although the PIV and CFD data had similar trends, the magnitudes were different. The reasons for these discrepancies include the fact that the oscillation period for the orifice jet could not be precisely identified and eliminated from the data and errors inherent in the methods used to estimate the local specific turbulent energy dissipation rate from the PIV data.

      PubDate: 2017-01-27T20:07:24Z
       
  • Profile of huge wave in gas–liquid churn flow
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Ke Wang, Jing Ye, Bofeng Bai
      The knowledge of wave profile of the huge waves is crucial for the thorough study on the pressure drop in churn flow, which is of great interest in many industries where such chaotic flow occurs. The literature lacks information on the profile of a huge wave under churn flow condition. Usually, hemispherical and sinusoidal shapes are employed to feature the general characteristic of the huge wave. No doubt, errors will be inevitably result. To explore this issue, we used a high-speed camera to capture a more detailed description of the huge wave in a 19mm i.d. tube under churn flow condition. The experimental results indicate that the ratio between wave length and wave amplitude is found to be about 5 irrespective of gas and liquid velocities. By analyzing the silhouette of the huge wave at its critical condition (stationary), we proposed a Gaussian function to describe such wave shape more accurately. Compared with the existing wave shapes, the Gaussian function qualitatively and quantitatively reproduces the evolution of the huge wave quite well whereas the sinusoidal function comparatively has the lowest precision in prediction. Though a far cry from the real wave shape, the hemispherical function is recommended to simplify the calculation on the basis of a simpler form but a sufficient accuracy.

      PubDate: 2017-01-27T20:07:24Z
       
  • Experimental study on droplet generation in flow focusing devices
           considering a stratified flow with viscosity contrast
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): Xiaoming Chen, Carolyn L. Ren
      High throughput analysis is highly demanded in a variety of chemical reactions. Droplet microfluidics offers unique advantages over traditional multi-well plate systems for high throughput analysis such as providing a confined and more controllable environment for single particle or cell analysis. Driven by the need to improve the efficiency of encapsulating one particle or cell into one individual droplet without complicating geometric and operating conditions, this study experimentally investigated the effects of viscosity contrast between two miscible fluids that together serve the dispersed fluid on the ordering of particles before they are encapsulated into droplets by another immiscible fluid. Five scenarios with different viscosity contrast were systematically considered and a physical model of droplet size for each scenario was developed based on experimental results and scaling laws. The five different scenarios include two with pure 10% glycerol and pure 80% glycerol as the dispersed phase, respectively, and three others where these two fluids are either side by side or one is accompanied by the other. Droplet size and formation period for these scenarios were compared and analyzed considering the same geometric and flow conditions. It is found that the stratified flow structures formed in the first junction by the two miscible fluids (10% and 80% glycerol solutions) strongly influence droplet formation dynamics such as droplet size and formation frequency. Each scenario finds its own applications. The scenario with 80% glycerol surrounded by 10% glycerol provides the optimized means for particle encapsulation. However, the scenario with two fluids side by side in the first junction generates droplets with high monodispersity for the largest range of flow ratios, which is useful for high throughput reactions involving different reagents.

      PubDate: 2017-01-20T20:04:41Z
       
  • Synthesis and characterization of sponge-like α-Fe microtubes
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): V.I. Mikhaylov, E.F. Krivoshapkina, V.A. Belyy, P.V. Krivoshapkin
      Sponge-like magnetic α-Fe microtubes have been prepared via reduction of α-Fe2O3 microtubes in hydrogen flow. α-Fe2O3 microtubes have been previously obtained by combined sol-gel and template methods. It is shown that the strongly acidic aqueous medium leads to specific interaction of ferric hydroxide nanoparticles with cellulose template. This contributes to the formation of α-Fe2O3 microtubes, which retain the features of the initial fibers structure. Both calcination at high temperature (1200°C) and reduction does not lead to the destruction of the tubular morphology. The resulting magnetic materials have a promising applications in biomedicine, as micro-reactors, microwave absorbing materials, easily recoverable from the reaction medium catalysts of various chemical reactions (including carbon nanotubes growth) and a component for creating new composite (e.g., metal-oxide) materials with improved performance characteristics.
      Graphical abstract image

      PubDate: 2017-01-20T20:04:41Z
       
  • Micromechanical analysis of flow behaviour of fine ellipsoids in gas
           fluidization
    • Abstract: Publication date: 18 May 2017
      Source:Chemical Engineering Science, Volume 163
      Author(s): J.Q. Gan, Z.Y. Zhou, A.B. Yu
      The macro-scale flow behaviour of granular materials in gas fluidization is governed by particle-particle and gas-particle interactions, which are affected significantly by particle size and shape. Understanding the micro-scale flow structure of fine non-spherical particles is essential for process design, optimisation and control. In this work, the combined approach of computational fluid dynamics for gas phase and discrete element method for particles is used to study flow and force structures of fine ellipsoids in gas fluidization. The results reveal that fine particles have vortex flow structure in fluidized beds, and the vortex flow becomes more significant particularly for oblate particles. The microscopic structure analysis demonstrates that when aspect ratio deviates from 1.0, the packed beds could experience compaction, and in expanded beds, the bed expansion ratio increases. The effect of particle size is investigated, showing that with the decrease of particle size, the mean coordination number decreases due to more significant role of van der Waals force. Ellipsoids exhibit higher orientation order which varies greatly with gas velocity and particle size. In fluidized beds, ellipsoids tend to flow in small projected area to the fluid flow direction to reduce the flow resistance. The bed expansion criteria established in the literature are confirmed still valid for ellipsoids, but the gas velocity range for expanded bed interval is much wider than spheres.

      PubDate: 2017-01-20T20:04:41Z
       
  • Agglomeration during spray drying: Airborne clusters or breakage at the
           walls?
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Víctor Francia, Luis Martín, Andrew E. Bayly, Mark J.H. Simmons
      Particle agglomeration, wall deposition and resuspension are inherent to many industries and natural processes, and often inter-connected. This work looks into their relation in a confined particle laden swirling flow. It investigates how the size of detergent powder spray dried in a swirl counter-current tower responds to changes in the air flow. Four sets of sprays are investigated under varying combinations of air temperature and velocity that cause the same evaporation. The use of high air velocities accumulates more of the droplets and dry powder in the chamber swirling faster, but it leads to creation of a finer product. Particle-particle and particle-wall contacts are made more frequent and energetic but in turn the swirl troughs the solids to the wall where deposits constantly form and break. Past PIV and tracer studies revealed that the rates of deposition and resuspension are balanced; the data discussed here indicate that the dynamic nature of the deposits is a major contributor to particle formation. In contrast with the usual assumption, the product size seems driven not by inter-particle contacts in airborne state but the ability of the solids to gain kinetic energy and break up a collection of clusters layering on the wall. As a result, the dryer performance becomes driven by the dynamic of deposition and resuspension. This paper studies the efficiency of limiting operation strategies and shows that a low temperature design concept is better suited to control fouling phenomena and improve capacity and energy consumption.
      Graphical abstract image

      PubDate: 2017-01-20T20:04:41Z
       
  • Promoting oxidative activity and stability of CeO2 addition on the MnOx
           modified kaolin-based catalysts for catalytic combustion of benzene
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Peng Yang, Jingrong Li, Shufeng Zuo
      In this paper, a new kaolin-based NaY-type zeolite crystal (KL-NY) material was synthesized through in-situ crystallization, and CeO2-modified KL-NY-supported manganese oxide catalysts (MnCeOx/KL-NY) were further prepared and investigated for benzene combustion. The texture-structure, surface morphology, dispersion of active components and the redox properties of the materials were systematically characterized and analyzed by the techniques of N2 adsorption-desorption, high resolution transmission electron microscopy (HRTEM)-energy dispersive spectroscopy (EDS) as well as the H2 temperature-programmed reduction (H2-TPR). The results showed that the calcinated and crystallized KL-NY support exhibited good thermal stability with large specific surface area and large pore volume. The MnCe/KL-NY catalysts exhibited excellent deep oxidation properties. Among them, 10%MnCe(9:1)/KL-NY displayed the highest catalytic activity and could completely oxidize low-concentration benzene at 260°C; its activity did not decrease after continuous reaction for 800 h, indicating its high potential for industrial application. The improved catalytic properties of the MnCe/KL-NY catalysts were mainly related to the higher oxidation state of MnOx and the preferable redox properties, resulted from the highly dispersion of CeO2 and MnOx on the surface of KL-NY as well as their strong interaction.
      Graphical abstract image

      PubDate: 2017-01-20T20:04:41Z
       
  • Understanding and identifying the oxygen transport mechanisms through a
           mixed-conductor membrane
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): P.-M. Geffroy, E. Blond, N. Richet, T. Chartier
      Recent developments in oxygen transport membranes have led to a selection of membrane materials or designs to achieve a judicious compromise between the oxygen flux, chemical stability and mechanical performance of membranes under operating conditions. This paper briefly describes the state of the art in the current understanding of oxygen transport through mixed-conductor membranes for oxygen separation. A better understanding of oxygen transport mechanisms, in particular, oxygen exchange at the membrane surface, leads to the identification of relevant key parameters that control the oxygen semi-permeation performance of the membrane. From a rational approach, key parameters are identified and discussed to identify promising membrane materials.

      PubDate: 2017-01-20T20:04:41Z
       
  • Sonocatalytic degradation coupled with single-walled carbon nanotubes for
           removal of ibuprofen and sulfamethoxazole
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Yasir A.J. Al-Hamadani, Chanil Jung, Jong-Kwon Im, Linkel K. Boateng, Joseph R.V. Flora, Min Jang, Jiyong Heo, Chang Min Park, Yeomin Yoon
      This study examined the degradation of pharmaceuticals ((PhACs), ibuprofen (IBP) and sulfamethoxazole (SMX)) using an ultrasonic (US) reactor at a 1000kHz frequency in the absence and presence of single walled carbon nanotubes (SWNTs). In the absence of SWNTs, maximum degradation of PhACs were achieved under high temperature; 55>35>25>15°C. In addition, the relatively higher degradation of IBP and SMX was obtained under acidic condition at pH 3.5 than pH 7 and 9.5; >99%, 79%, and 72% for IBP and >99%, 75%, and 65% for SMX, respectively. However, H2O2 production increased from 77μM (no SWNTs) to 115μM in the presence of SWNTs (45mg/L) at pH 7. In addition, the removal of IBP and SMX significantly increased under US/SWNTs reaction conditions than US and SWNTs only reactions. The removal of IBP and SMX was 57% and 48% under SWNTs (adsorption) reactions, 77% and 70% under US reactions, and 97% and 92% under US/SWNTs reactions, respectively. This study evaluated the effect of temperature, pH, SWNTs, and physiochemical properties of selected PhACs under US process. In addition, the adsorption molecular modeling was validated with the experimental results.
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      PubDate: 2017-01-20T20:04:41Z
       
  • New method of determination of intrinsic kinetic and mass transport
           parameters from typical catalyst activity tests: Problem of mass transfer
           resistance and diffusional limitation of reaction rate
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): P.J. Jodłowski, R.J. Jędrzejczyk, A. Gancarczyk, J. Łojewska, A. Kołodziej
      A question arises whether the kinetic parameters derived from the Arrhenius equation presented in the literature in fact reflect intrinsic kinetics or are influenced by diffusional effects. It is commonly accepted that diffusion can not only influence (reduce) the reaction rate but also change the observed kinetic constants and reaction order. In this study the limitation of reaction rate (n-hexane catalytic combustion) was observed even at moderate temperatures during experiments performed in a Continuous Stirred Tank Reactor (CSTR), gradientless reactor dedicated to determination of reaction kinetics. In this study a numerical method of the separation of intrinsic kinetics from mass transport effects has been proposed for an experiment executed under significant mass transfer resistance. It was tested using different carrier types (steel sheets and woven wire gauzes) and catalyst formulations for two combustion reactions: of n-hexane and methane. The intrinsic kinetic parameters derived in this way were then used for the numerical simulations of three types of structured reactors filled with: woven and knitted wire gauzes and monolith in terms of the optimization of a reactor length for combustion reactions. The performed simulations showed that the application of woven gauzes as the reactor internals can give rise to substantial decrease of the reactor length even by 10 times for both methane and n-hexane catalytic combustion reactions.
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      PubDate: 2017-01-20T20:04:41Z
       
  • Asphalt-derived high surface area activated porous carbons for the
           effective adsorption separation of ethane and ethylene
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Wanwen Liang, Yufan Zhang, Xingjie Wang, Ying Wu, Xin Zhou, Jing Xiao, Yingwei Li, Haihui Wang, Zhong Li
      We reported novel asphalt–based activated carbons (A-ACs) with high C2H6/C2H4 adsorption capacity and selectivity. A series of A-ACs were prepared by a one-step preparation method and characterized. The adsorption performances of A-ACs for ethane/ethylene were examined. Results showed that the sample A-ACs prepared at 800°C and the KOH/asphalt ratio=4 exhibited ultra-high BET area of 3111m2/g and its pore volume reached 1.92cm3/g. Their surface O and N contents gradually decreased with activation temperature or KOH/asphalt ratio at which A-ACs were prepared. More interestingly, A-ACs showed significantly preferential adsorption of C2H6 over C2H4. It could be ascribed to the stronger interaction of C2H6 with the surfaces of A-ACs by hydrogen bonds compared to C2H4, which were revealed by Density functional theory calculation. Its C2H6 adsorption capacity was up to 7.2mmol/g at 100kPa and 25°C and its C2H6/C2H4 adsorption selectivity for typical cracked gas mixture (15:1 ethylene/ethane) was in the range of 3.2–16.3 at the pressure below 100kPa, higher than the most reported ethane-adsorbents. Additionally, the isosteric heat of ethane and ethylene adsorption on A-ACs were lower than those on π-complexation adsorbents. Therefore, these excellent adsorption properties would make A-ACs as a type of promising adsorbents for adsorption separation of C2H6/C2H4.
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      PubDate: 2017-01-13T06:22:31Z
       
  • Analysis of powder rheometry of FT4: Effect of air flow
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Wenguang Nan, Mojtaba Ghadiri, Yueshe Wang
      Understanding of particle flow behaviour as a function of strain rate is of great interest in many items of equipment of industrial processes, such as screw conveyors, impeller mixers, and feeders. The traditional commercial instruments for bulk powder flow characterisation, such as shear cells, operate at low shear strain rates, and are not representative of unit operations under dynamic conditions. In recent years, the FT4 powder rheometer of Freeman Technology has emerged as a widely used technique for characterising particle flow under dynamic conditions of shear strain rate; yet little is known about its underlying powder mechanics. We analyse the effect of gas flow on the flow behaviour of cohesionless particles in FT4 both experimentally and by numerical simulations using the combined discrete element method (DEM) and computational fluid dynamics (CFD). The results show that the effect of gas flow on the flow energy could be described by the resultant fluid-induced drag on the particles above the blade position as the impeller penetrates the bed. The strain rate in front of the blade is mainly determined by the impeller tip speed, and is not sensitive to the gas flow and particle size. The flow energy correlates well with the shear stress in front of the blade. They both increase with the strain rate and are significantly reduced by the upward gas flow.
      Graphical abstract image

      PubDate: 2017-01-13T06:22:31Z
       
  • The frequency of periodic structures in vertical pneumatic conveying of
           large particles
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Barry J. Azzopardi
      The transport of larger particles, defined as type D in the classification of Geldart (1973), by pneumatic conveying, is characterised by periodic structures, namely slugs. The frequency of these slugs in vertical pipes shows a trend similar to that seen for equivalent structures in gas-liquid flows. A simple equation has been derived to specify the apparent viscosity of the dense particle areas. From the non-dimensional relationship describing the frequency, its dependence on different variables can be identified. It can be inferred that pressure will not have a strong effect on frequency. There is a complication when the piping consists of a horizontal pipe followed by a bend and a vertical section. If there is slug flow in the horizontal pipe, the frequency in the vertical pipe could be the same as that in the horizontal section.
      Graphical abstract image

      PubDate: 2017-01-13T06:22:31Z
       
  • Pressure drop in packed beds of angular parallelepipeds, including the
           effects of particle interference
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Élizabeth Trudel, William Hallett
      Pressure loss measurements are reported in packed beds of seven different shapes of angular parallelepiped, ranging from nearly cubical particles to thin flat chips, and compared with a number of available correlations, most of which underpredicted the pressure loss. All particle types when packed in the bed were found to overlap each other to some degree, and the extent of this was estimated from photographs, from which the average particle surface area effectiveness η was found to range from 0.69 to 0.85. The pressure loss correlation of Nemec and Levec (2005) was modified to include the effects of particle overlap, and values of η deduced by fitting to the measurements. The resulting values agreed well with those estimated from photographs, indicating that a pressure loss test can be used to assess particle overlap in a bed of known particle geometry. The range of Reynolds numbers covered was about 150–900. This is expected to be useful in assessing effective surface areas for heat and mass transfer and chemical reaction in packed beds.

      PubDate: 2017-01-13T06:22:31Z
       
  • Effect of sintering on the reactivity of copper-based oxygen carriers
           synthesized by impregnation
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Juan C. Maya, Farid Chejne, Suresh K. Bhatia
      A grain model based on population balances for redox reactions of copper-based oxygen carriers is developed. It considers the effects of grain size distribution and sintering, and a new expression for the aggregation frequency, which takes into account the sintering mechanisms and synthesis method, is deduced. In order to validate the model, six copper-based oxygen carriers were synthesized by excess wet impregnation and by incipient impregnation. They were characterized by BET surface area, BJH porosimetry, and SEM microscopy. Model results were compared with experimental data acquired by thermogravimetry during several redox cycles and the model was able to predict the conversion drop over the course of redox cycles due to sintering. It was found that copper-based oxygen carriers synthesized by incipient impregnation are more strongly affected by sintering than those prepared via excess wet impregnation, and finally it is shown that metallic copper sinters during oxidation, resolving a controversy in this regard that has existed in the literature.

      PubDate: 2017-01-13T06:22:31Z
       
  • Three-dimensional numerical study of heat transfer and mixing enhancement
           in a circular pipe using self-sustained oscillating flexible vorticity
           generators
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Samer Ali, Charbel Habchi, Sébastien Menanteau, Thierry Lemenand, Jean-Luc Harion
      In this paper, heat transfer and mixing performances are studied using three-dimensional numerical simulations of fluid-structure interactions. To this aim, a multifunctional heat exchanger/reactor geometry is investigated, consisting of a circular pipe where five arrays of four equally spaced trapezoidal vortex generators are inserted and inclined in a reversed position opposite to the flow direction with an angle of 45° with respect to the pipe wall. A periodic rotation of 45° is applied to the tabs arrays. Two cases are numerically studied: one using flexible vortex generators (FVG) that deform due to fluid forces applied on the structures and the other using conventional non deformable rigid vortex generators (RVG). For the FVG configuration, the tabs oscillate without addition of any external source of energy except that of the fluid flow itself, leading to a passive but dynamic way to perform vortex formation to disturb the flow. Both flow regimes are laminar with a constant Reynolds number of 1500. The flow structures are analyzed using the proper orthogonal decomposition (POD) technique and the effect of tabs oscillation on vortices creation, suppression and dislocation is highlighted. The effect of self-sustained free elastic tabs oscillation on heat transfer and mixing performances is numerically investigated by comparing the FVG with its corresponding RVG configuration. The Nusselt number comparison shows that the free tabs oscillation can improve the overall heat transfer of about 118% with respect to an empty pipe whereas it is about 97% for the RVG study. Finally, to assess the mixing performance, the transport of a passive scalar initially divided into two different concentrations in the pipe is numerically analyzed through the mixing index value. The FVG configuration shows a drastic improvement of the mixture quality at the exit of the pipe with an increase of 195% with respect to the RVG case, leading to much shorter and compact mixers and reactors.

      PubDate: 2017-01-13T06:22:31Z
       
  • Evaluation of two-group interfacial area transport equation model for
           vertical small diameter pipes against high-resolution experimental data
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Akshay J. Dave, Annalisa Manera, Matthias Beyer, Dirk Lucas, Matthew Bernard
      Two-phase flow is ubiquitous in industrial, chemical and thermal plants alike. The current state-of-the-art system-code model for predicting fluid transport in two-phase flows is the two-fluid model. In the two-fluid transport model, the coupling of mass, momentum and energy transfer between phases is highly dependent on interfacial area transfer terms. Several research efforts in the past have been focused on the development of an interfacial area transport equation model (IATE) in order to eliminate the drawbacks of static regime flow maps currently used in best-estimate thermal-hydraulic system codes. The IATE attempts to model the dynamic evolution of the vapor/liquid interface by accounting for the different interaction mechanisms affecting gaseous phase transport. The further development and validation of IATE models has been hindered by the lack of adequate experimental data in regions beyond the bubbly flow regime. At the Helmoltz-Zentrum Dresden-Rossendorf (HZDR) experiments utilizing wire-mesh sensors have been performed over all flow regimes, establishing a database of high-resolution (in space and time) data. A 52.3mm diameter pipe with a 16 by 16 wire-mesh sensor operating at 2.5kHz is utilized in the air-water experimental database used in this work. There are a total of 37 tests (with varying superficial gas and liquid velocities, at approximately 0.25MPa). Analysis of IATE performance in the bubbly flow and slug flow regimes is presented. The performance of the Fu-Ishii two-group IATE model is evaluated. In all regions, the interfacial area concentration for small bubbles is predicted well. The model performs poorly in high void fraction regimes, in which large irregularly shaped bubbles are present. The interaction mechanisms that support and deter performance of the IATE model are highlighted. A sensitivity analysis indicates modification of the group-2 wake entrainment coefficient may extend the validity of the Fu-Ishii model. An optimization study is presented to further explore improving IATE performance. It is concluded that the availability of accurate data at high void fractions from the HZDR facility provides a path to improve IATE performance.

      PubDate: 2017-01-13T06:22:31Z
       
  • Liquid-like granular film from granular jet impact
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Zhe-Hang Shi, Wei-Feng Li, Wen-Wei Qian, Hai-Feng Liu, Fu-Chen Wang
      Dynamic behaviors of dense granular jets impacting a flat target are experimentally studied and numerically simulated using the Discrete Element Method. Effects of the granular jet velocity (u 0 ⩽6.5m/s), the particle diameter (82⩽ d ⩽350μm), the jet diameter (1⩽ D ⩽12mm), and the volumetric solid content ratio of the granular jet (0.05⩽ x p <0.62) on the flow patterns are investigated. Two patterns were identified: the thin, liquid-like granular film and the diffuse pattern. The profile and thickness of granular films have been characterized. The transition critical parameters and maps of the two patterns are obtained in this work. Results show that the regimes of the granular jet impact are primarily determined by the ratio of jet diameter to particle diameter (D/d) and solid content ratio (x p). A compacted dead zone over the target forms with large D/d and x p, which subsequently causes rapid interparticle inelastic collisions and circular motion of the granular film.
      Graphical abstract image

      PubDate: 2017-01-06T02:33:39Z
       
  • Techno-economic analysis and environmental impact assessment of
           lignocellulosic lactic acid production
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Asfaw Gezae Daful, Johann F. Görgens
      Lignocellulosic Lactic acid (LA) production is considered for the diversification and value addition to an existing sugar industry by annexing a biorefinery using lignocellulosic residues, sugarcane bagasse and leaves (SCBL). In biorefinery, the hemicellulose (C5 sugars) and cellulose (C6 sugars), resulting from lignocellulosic matrix fractionation, can be converted into building block chemicals and fuels by biotechnological or chemical pathways. To co-produce LA with other fuels and chemicals from SCBL, it is important to determine whether LA production from C5 or C6 sugars should be preferred, based on economic viability and environmental impacts. In this paper we developed six process scenarios for LA production from either the hemicellulose liquid fraction and cellu-lignin solid fractions of SCBL after steam explosion pretreatment, based on 200tonne/day of SCBL feed. The lignocellulose fraction not used for LA production will be used for integrated production of other marketable products in a biorefinery. Scenarios S1, S3, & S5 use the hemicellulose liquid fraction as feed for LA production, while scenarios S2, S4, & S6 use the cellu-lignin solid fraction. Two scenarios, S1 & S2, use Ca(OH)2 as neutralizer in fermentation, resulting in co-production of gypsum as solid waste, scenarios S3 and S4 use an isolated acid-tolerant thermophilic bacteria, Bacillus coagulans isolates for fermentation, thus avoiding the need for neutralization, while Scenarios S5 and S6 use Mg(OH)2 as neutralizer in fermentation, with recycling of Mg(OH)2. LA was separated and purified from the fermentation broth by reactive distillation. The six process scenarios were modeled and simulated by Aspen Plus® with the resulting mass & energy balance and equipment-sizing used as inputs to economic analysis and environmental impact assessment. Standard life cycle assessment (LCA) method is used in SimaPro® for environmental impact quantification. Cellulose based processes have larger LA production rates than the hemicellulose based processes, for the same flow rate of SCBL, which impacts on their total capital investment (TCI), operating cost (OPEX) and revenues for the same process technology. Increases of 7.08%, 58.13%, 12.04% and 60% in TCI, revenue, OPEX and LA production rates, respectively were observed in moving from S1 to S2. Similar increases of 10.88%, 86.52%, 18.52% and 91.07% in TCI, revenue, OPEX and LA production respectively in moving from S3 to S4. An increment of 10.08%, 61.57%, 18.32% and 63.90% in TCI, revenue, OPEX and LA production respectively was also found in moving from S5 to S6. Scenarios S3 and S4 are found to have lower TCI and OPEX but their production rate is low as well making them economically less attractive with internal rate of return (IRR) of 9.13% and 15.23% respectively. While S1 and S2 have IRR of 13.11% and 19.4% respectively and yet higher TCI and OPEX. S5 and S6 have the highest IRR, 14.72% and 21.28% respectively with TCI and OPEX of way below their equivalent scenarios S1 and S2 respectively. From the environmental point of view S1 and S2 are found to be environmentally less friendly with higher environmental burdens in almost all impact categories considered. Gypsum free scenarios, S5 and S6, are found to be the most attractive processes from both economic and environmental points of view, with S6 being superior than S5.

      PubDate: 2017-01-06T02:33:39Z
       
  • Delta-operator-based adaptive model predictive control and online
           optimization of a natural gas liquefaction process
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Wangyun Won, Kwang Soon Lee
      The production of liquefied natural gas (LNG) is an energy-intensive process. The required temperature is approximately −160°C at atmospheric pressure. As a result, energy efficiency is the major concern in the process operation. Addressing this issue, we propose a new energy optimizing control system for the LNG process. It consists of an online steady-state optimizer, a model predictive controller (MPC), and a model parameter estimator. The optimizer computes optimum compression ratios and warm-end delta-temperature, while the MPC steers the process toward the target operating conditions. Particularly, the MPC was developed in a delta-form for better numerical stability during continuous operation of a multiple-input multiple-output system with widely distributed time constants. To minimize process perturbation by identification experiments, the model for controller design was derived from a rigorous LNG simulator. To cope with the model error from the true system, a small number of tunable parameters were introduced so that they can be corrected online by model parameter estimator during the process operation. The performance of the developed operation system was demonstrated in a numerical 100ton-per-day LNG plant, which was precisely constructed to replicate an actual plant in Incheon, Korea.

      PubDate: 2017-01-06T02:33:39Z
       
  • Covalent organic polymer modified TiO2 nanosheets as highly efficient
           photocatalysts for hydrogen generation
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Qingqing Yang, Peng Peng, Zhonghua Xiang
      Splitting water into hydrogen driven by solar energy is considered as one of the major strategies to provide clean energy. TiO2-based photo-catalysts have attracted everlasting interests due to low cost sources and excellent stability. However, the wide band gap and limited quantum efficiency of TiO2 hinder its application. Herein, a novel photocatalyst for hydrogen evolution was initially prepared by modification of TiO2 nanosheets with covalent organic polymer (i.e., COP-64). The COP-64 not only can provide more reaction active sites by increasing the specific surface area of the pristine TiO2 nanosheets, but also improve light harvesting in visible light region. Moreover, the suitable energy level of COP-64 provides charge transfer channels and favors the electron transfer, which greatly inhibits the combination of photogenerated electrons (e−) and holes (h+) in the hybrid system. Particularly, the corresponding hydrogen production rate of the hybrids reaches 15.02mmolh−1 g−1, which exceeds 63% compared with that of pristine TiO2 nanosheets (9.20mmolh−1 g−1).
      Graphical abstract image

      PubDate: 2017-01-06T02:33:39Z
       
  • Extrapolation of surface tensions of electrolyte and associating mixtures
           solutions
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Hailong Chen, Zhaomin Li, Fei Wang, Zhuangzhuang Wang, Gao Zhihan
      A new surface tension model is proposed, based on the Gibbs phenomenological surface-phase method, coupled with Ion-based Statistical Associating Fluid Theory (Ion-based SAFT2). The model was used to extrapolate the surface tensions of aqueous electrolyte solutions and mixed electrolyte solutions, as well as systems of associating mixtures at different temperatures and concentrations, and was found to give good agreement with experimental data from the literature.

      PubDate: 2017-01-06T02:33:39Z
       
  • Experimental study of particle evolution characteristics in an opposed
           multi-burner gasifier
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Qing Zhang, Yan Gong, Qinghua Guo, Zhicun Xue, Fuchen Wang, Guangsuo Yu
      Based on a bench-scale opposed multi-burner (OMB) gasifier and advanced visualization techniques, the particle evolution characteristics in the gasifier was studied. Particle images of different focusing planes were obtained by optical sectioning tomography (OST) method. Particle types and the principles of transformation between them, particle shape and particle size distribution (PSD), particle fragmentation characteristics were statistically analyzed after image processing. The results show that the burner plane contains all of the particle types, most of them are high temperature particle without wake (HTP), low temperature particle without wake (LTP), high temperature particle with high temperature wake (HTP-HTW) and low temperature particle with high temperature wake (LTP-HTW). Particle shapes in the burner plane are mainly round or round-like. The particle fragmentation process in the burner plane is violent and usually accompanied by sudden bursts that would result in the change of particle motion status, but the probability of which is relatively low (only about 7%). The space between 100mm and 300mm above the burner plane is the main regions of particle pyrolysis, particle types are mainly the low temperature particle with low temperature wake (LTP-LTW). Particles at 100mm above the burner plane have a higher fragmentation probability (10.53%) than that at 200mm (9.51%) and 300mm (8.73%) above the burner plane because of the more intense pyrolysis. In these regions, particle shapes become more irregular and the median particle diameter (D50) are slightly increased. There are plenty of LTP in the space between 400mm above the burner plane to the refractory dome. The probability of fragmentation around 400mm (16.84%), 500mm (11.35%) and 580mm (9.32%) above the burner plane are all higher than the probability around 100mm, 200mm and 300mm above the burner plane, which indicates that the particle fragmentation has more probability to take place in the char gasification stage than in the pyrolysis stage in the OMB gasifier. The closer to the refractory dome, the less the number of large particle is and the smaller the D50 is. About 85% of the particles near the refractory dome have a diameter less than 500μm.

      PubDate: 2017-01-06T02:33:39Z
       
  • Modeling of a tubular solar reactor for continuous reduction of CeO2: The
           effect of particle size and loading on radiative heat transfer and
           conversion
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): P.J. Valades-Pelayo, H.I. Villafán-Vidales, H. Romero-Paredes, C.A. Arancibia-Bulnes
      A solar multi-tubular reactor for non-stoichiometric reduction of CeO2 is modeled under continuous operation. An aerosol, consisting on CeO2 particles and Argon, flows upwards through the reactor vertical tubes. Heat, mass and radiation transfer phenomena are efficiently implemented in an axisymmetric domain by using multi-mesh, multi-step, Finite-Volume and Monte Carlo methods. Reaction, particle diffusion, conduction, forced convection as well as radiation absorption, emission and anisotropic scattering are considered. The kinetic model for the non-stoichiometric reduction of CeO2 is taken from Ishida et al. (2014). Model results at steady-state focus on the effect of changing particle loading and diameter at different average residence times. For particle diameters of 1–20μm, increasing particle size favors uniform radiation absorption, minimizing temperature gradients. Finally, for an outer tube surface temperature of 2500K, a particle loading of 0.1kg/m3 and average residence time of 30–60s are recommended.

      PubDate: 2017-01-06T02:33:39Z
       
  • Modeling of multiphase reaction and slag flow in single-burner coal water
           slurry gasifier
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Jianliang Xu, Zhenghua Dai, Haifeng Liu, Liangyu Guo, Feng Sun
      The slag flow properties and temperature distribution have a critical influence on the lifetime of refractory bricks. A comprehensive model has been developed to simulate a multiphase flow and reaction process within the spatial region and refractory wall, and is applied to a study on the multiphase flow characteristics of a single-burner entrained-flow gasifier. The gasifier performance, gas temperature distribution, and outer surface temperature distribution of the wall are compared with industry measurement data. The simulation results are in good agreement with the industrial data. The capture efficiency of the refractory wall is approximately 91%, and 82% of the particles are trapped by the wall. The distribution of the gas temperature near the refractory wall, the slag surface temperature, and the refractory wall surface temperature aresimilar. The slag surface temperature first decreases from top to bottom, and then increases to the highest temperature at 2.2D. The slag attack rate coincides with the refractory brick corrosion rate. The refractory surface temperature, molten slag fluidity, and molten slag flow rate have a significant impact on the refractory brick corrosion rate. No solid slag layer is present on the refractory bricks, and the molten slag layer thickness increases from 0 to 5mm along the flow direction. In the molten slag layer, the non-dimensional slag velocity profile shows a self-similarity and follows a parabolic equation.

      PubDate: 2017-01-06T02:33:39Z
       
  • Transport-reaction-permeation regimes in catalytic membrane reactors for
           hydrogen production. The steam reforming of methane as a case study
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): M.A. Murmura, S. Cerbelli, M.C. Annesini
      Catalytic reactors equipped with dense metallic membranes for hydrogen production are attracting increasing interest in view of their potential to overcome yield limitations associated with chemical equilibrium. A transport-reaction-permeation isothermal model, fully coupled with momentum transport through the packed bed, is here considegd for the species participating to the methane steam-reforming reaction in an annular catalytic reactor fed by a pre-reformed (equilibrium) mixture. Model predictions are validated by comparison with experimental data available in the literature. Large variations of the mixture density are found as a consequence of nonuniform composition profiles, which, in turn, trigger sizeable radial convective fluxes of hydrogen towards the membrane. Nonlinearities associated with chemical equilibrium, reaction kinetics, membrane permeation, and density dependence on composition interact with one another, making the overall equipment response markedly complex. A thorough dimensionless analysis of the response of the reactor vs the operating pressure is carried out, which shows the occurrence of non-monotonic behavior characterized by a maximum of efficiency associated with a critical pressure value. A scaling law of critical efficiency vs the main dimensionless parameters is proposed, which can provide a rationale for the design of reactor geometry and operating conditions.

      PubDate: 2017-01-06T02:33:39Z
       
  • Analysis of solubility, absorption heat and kinetics of CO2 absorption
           into 1-(2-hydroxyethyl)pyrrolidine solvent
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Helei Liu, Moxia Li, Raphael Idem, Paitoon (PT) Tontiwachwuthikul, Zhiwu Liang
      The CO2 absorption performance of aqueous 1-(2-hydroxyethyl)pyrrolidine (1-(2-HE)PRLD) was studied with respect to kinetics (i.e., in terms of the pseudo-first-order rate constant (k o) and second-order reaction rate constant (k 2), obtained using the stopped-flow apparatus). CO2 equilibrium solubility and heat of CO2 absorption were evaluated at the temperature range of 293–313K in the 1-(2-HE)PRLD concentration range of 0.20–1.00mol/L for kinetics and at 2M for CO2 solubility. The values of k o were then represented using the base-catalyzed hydration mechanism, which gave an acceptable AAD of 10%. In addition, Brønsted plots of k 2 vs. pKa were developed to predict k 2 using pKa values of various tertiary amines. In addition, the CO2 equilibrium solubility and CO2 absorption heat were obtained in this work. Based on a comparison with other amines such as MEA, MDEA and 1DMA2P, 1-(2-HE)PRLD showed better performance in terms of CO2 equilibrium solubility (DEAB>1-(2-HE)PRLD>1-(2HE)PP>1DMA2P>MDEA>MEA>DEA), kinetics (MEA>DEA>DEAB>1-(2-HE)PRLD>1-(2-HE)PP>DMMEA>1DMA2P>MDEA.) and CO2 absorption heat (MEA>DEA>MDEA>DEAB>1-(2-HE)PRLD>1-(2HE)PP>1DMA2P). Therefore, 1-(2-HE)PRLD could be considered as a good alternative solvent for CO2 capture. A correlation between kinetics and heat of CO2 absorption has been developed to guide the design of what can be considered to be ideal amine solvents for CO2 capture.

      PubDate: 2017-01-06T02:33:39Z
       
  • Modeling an effect of pipe diameter on turbulent drag reduction
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Dmitry Eskin
      An effect of pipe diameter on drag reduction in a pipeline flow is taken into account by an adjustment of the modeling approach of Yang and Dou (2005). For validation of this adjustment, computational results obtained by the drag reduction models of Eskin (2014) and Yang and Dou (2010), based on the Yang and Dou approach, are compared with the experimental data of Virk (1975).

      PubDate: 2017-01-06T02:33:39Z
       
  • Simulation of microwave thin layer drying process by a new theoretical
           model
    • Abstract: Publication date: 27 April 2017
      Source:Chemical Engineering Science, Volume 162
      Author(s): Jun Jiang, Leping Dang, Cheong Yuensin, Hongsing Tan, Bochen Pan, Hongyuan Wei
      Various methodologies have been proposed in literature on modeling microwave drying process. However, in these methodologies moisture diffusion is normally considered in the presence of intensive microwave energy. In the present study, a new theoretical model was developed to simulate microwave drying of thin layer particulate solids, based on the consideration that moisture diffusion along material layer could be ignored due to rapid evaporation under intensive microwave energy. The model was solved numerically by using finite difference method and validated against experimental data. Results indicated good agreement between the model and experimental data, thus providing confidence in the modeling approach. For the system investigated in this study, it was demonstrated that an 80% reduction in drying time was achieved with approximately fivefold increase in microwave power (109–543W). Furthermore, it was also demonstrated that the drying rate was the maximum corresponding to the optimal layer thickness in microwave thin layer drying process. Qualitative analysis explained the optimal thickness phenomenon using principles of heat and mass transfer. Finally, the validated model was used to predict moisture and temperature distributions along the entire material layer.

      PubDate: 2017-01-06T02:33:39Z
       
 
 
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